Accounting for Shared-based Payments - Schedule of Stock Option Activity (Details) - USD ($)		3 Months Ended		12 Months Ended
	Nov. 20, 2009	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Remaining Contractual Term
Stock based compensation expense		$ 2,897,000	$ 1,202,000
Proceeds from exercise of stock options		$ 329,000	$ 0
Stock Options | $0.44-9.12
Number of Options
Balance outstanding, beginning of period (in shares)		27,867,171
Balance outstanding, end of period (in shares)		27,784,548		27,867,171
Exercisable at the end of the period (in shares)		13,913,788
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 0.44			$ 0.44
Exercise price, high end of the range (in dollars per share)		9.12			$ 9.12
Weighted Average Exercise Price Per Share
Balance outstanding, beginning of period (in dollars per share)		3.78
Balance outstanding, end of period (in dollars per share)		3.91		$ 3.78
Exercisable at the end of the period (in dollars per share)		$ 3.70
Intrinsic Value
Outstanding		$ 31,558,000		$ 65,618,000
Exercisable, end of period		$ 17,227,000
Weighted Average Remaining Contractual Term
Balance		6 years 10 months 13 days		7 years 1 month 6 days
Exercisable at the end of the period		5 years 8 months 27 days
Stock Options | $0.44-9.12 | Contingent vesting
Weighted Average Remaining Contractual Term
Grant date fair value	$ 28,600,000
Stock based compensation expense	$ 0
Stock Options | $4.57-6.77
Number of Options
Granted (in shares)		843,500
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 4.57
Exercise price, high end of the range (in dollars per share)		6.77
Weighted Average Exercise Price Per Share
Granted (in dollars per share)		$ 6.06
Stock Options | $1.90-5.34
Number of Options
Exercised (in shares)		(89,978)
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 1.9
Exercise price, high end of the range (in dollars per share)		5.34
Weighted Average Exercise Price Per Share
Exercised (in dollars per share)		$ 1.90
Intrinsic Value
Exercised		$ 203,957,000
Stock Options | $2.83-7.91
Number of Options
Forfeited (in shares)		(836,145)
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 2.83
Exercise price, high end of the range (in dollars per share)		7.91
Weighted Average Exercise Price Per Share
Forfeited (in dollars per share)		$ 4.50